Pipe heater construction



March 17, 1936. G. w. WATTS ET AL 2,034,362

PIPE HEATER CIONSTRUCTION Filed Dec. so, 1953 s Sheets-Sheet 1 to v v Inventors:- N 580738 N WQZZ5 We Z ZezcefiMczthe W5 7 PDMLi. I

ATTORNEY March 17, 1936.

G W. WATTS ET AL PIPE HEATER CONSTRUCTION Filed Dec. 50, 1955 3 Sheets-Sheet 2 March 17, 1936. G. w. WATTS ET AL I PIPE HEATER CONSTRUCTION Filed Dec. 30, 1935 5 Sheets-Sheet 3 fn0ent0r.5:- 6607199?! Wczizis WallaceliMaZ/wma BY IBMQ'L m ATTORNEY Patented Mar. 17, 1936 PIPE HEATER CONSUCTIION George W. Watts, Whiting, Ind, and Wallace B. Mathews, Chicago, Ill., assignors to Standard Oil Company, Chicago, 111.,

Indiana a corporation of Application December 30, 1933, Serial No. 704,774 Claims. (01.12%356) This invention relates to improvements in pipe heater construction and more particularly to a novel chamber and tube arrangement therefor.

Among the problems encountered in pipe heater 5 construction is that of providing for uniform distribution of heat for the tubes on the walls and roof of the combustion chamber and of providing for maximum heat transfer by convection to the tubes in the convection section. In the conventional type of heater employing a combustion chamber and a single convection section separated from the former by a bridge wall, the hot gases from the burners must naturally flow in the direction of the bridge wall where, after passing .over the wall, they are drawn downwardly through the convection section and into asuitable flue provided therefor. This functioning of the heater usually results in a decrease in the amount of heat to which the tubes on the remote wall of the combustion chamber and adjacent roof portion are subjected. Furthermore, attempts to increase the convection section area, in the conventional pipe heater, to obtain higher efiiciency in heat transfer results in serious disadvantages such as the lengthening of the distance between the burnas and the top of the bridge wall with consequent decrease in radiant heat transfer, particularly with respect to the upper wall tubes and roof tubes or in the necessity for providing. in

3 creased draft at the flue to cause adequate draft overcoming the relatively high head of gas thus formed in the. convection section. If an adequate draft is not provided at the top of the heater, leaks in the heaterwsetting would/be outward instead of inward and the damage to the brick heater walls might be serious.

An object of our'invention is to provide an improved pipe still wherein the distribution of- 40 heat to the radiant tubes in the combustion chamber is uniform, thereby eliminating the so called dead spaces in the chamber and avoiding the overheating of certain of the tubes with consequent coke disposition. Another object is to provide a. pipe still as described wherein increased at the top of the bridge wall for the purpose of following specification and claims, and after consideration of the drawings forming a part of the specification wherein:

Fig. 1 is a horizontal sectional view of a pipe still constructed in accordance with the invention; 5

I Fig. 2 is a vertical sectional view along the line IIII of Fig. 1; and

Fig. '3 is a diagrammatic view of the tube arrangement employed. V

In general, the pipe still selected for illustration comprises, a combustion chamber A provided with burner openings B, through which fuel such as oil and gas, or pulverized carbonaceous fuel may be admitted to the combustion chamber, a pair of opposed convection chambers C separated from 15 the combustion chamber by bridge walls D, tubes E within the convection sections C, radiant wall tubes F in substantially horizontal array upon the four walls of combustion chamber A, and roof tubes G- located upon the roof of the combustion 29 chamber.

The side walls, roof structure, and lateral Wall support may be substantially that employed in the construction of aconventional pipe still, the

inner walls being of brick of highheat resistant qualities, at places directly subjected to hot gases, steel buckstays 2 to retain thewalls in proper alignment and form, and a fabricated steel roof support 3 for providing lateral support to the side walls and for supporting the roof structure. 30

The four corners of the combustion chamber A are preferably of re-entrant design as shown at t, thus to provide in combination with insulated metal doors 5 vertical header boxes within which are located the headers 6 forming the joints between adjacent horizontal runs of" the radiant tubes F. This construction greatly facilitates removal and cleaning of radiant tubes, two divergent tube rows being accessible at each header box.

Flues l0 communicate with the lower region of each of the convection sections C thereby to cause the hot gases and products of combustion to flow uniformly from the combustion chamber in equally divided streams over the opposed bridge walls D and through the, array of convection tubes E. In the event that operating conditions tend to favor an increase in draft through one of the convection sections. flue dampers may be employed toretain a balance in flow distribu-- tion throughout the several convection sections;

In a manner similar to the headers. 6; the

I headers l for the convection tubes E are located at opposite ends of the convection section strucconvection sections toa manifold I2 where the the convection sections C in double pass although it should be understood that the precise multiple pass arrangement and dimensions of the tubes may be left to the discretion of the designing engineer in view of the particular purposes for which the still is to be used.

With reference to Fig. 3 we have illustrated therein the flow diagram and the tube arrangem'ent. It will be noted that the fluid input to the still enters simultaneously through two manifolds l I, each connected withthe lowermost rank of the groups of convection tubesE, whereupon the course of flow is upwardly through the fluid streams, are joined and directed through the upper rank l3 of the roof tubes G. Flow from the upper bank of the roof tubes G'-l 3 is directed downwardly through a pipe I to the lower of the spiral arrangement of wall tubes F and upwardly through the tubes, about the walls of the combustion chamber, and thereafter through the lower rank l 5 of the roof tubes G and finally toatransfer line l6.

In the pipe still illustrated the convection tubes are of three and one-half inch'outside diameter and oneuarter inch wall size, whereas the ra-' diant tubes both wall and roof have an outside diameter of flve and one-quarter inches and a three-eighthinch wall. Obviously the sizes and wall thickness of the various tubes may be altered to suit specific operating requirements.

In the heater illustrated we have shown quad-.

ruple pass through the convection tube sections and single pass through the wall and rooftubes, arranging each of they convection tube assemblies in the two convection sections in double pass for this purpose. By this arrangement the mass velocity of the fluid in the convection tubes may be substantially less than that of the, fluid in the radiant tubes notwithstanding that the surface areaof the tubes with respect to the fluid contents the convection system is greater than that in the radiant tube section. Thus high efficiency in heat absorption may be attained in from the direct radiant heat of the bumers.'

efficiency over the ordinary type of pipe still prlmarily because the heat losses are materially reduced. This feature is due in part to'the distribution of the convection sections about the major walls of the furnace thereby shielding the walls Further by virtue of the fact that opposite and laterally disposed convection sections and fines are employed flame impingement is precluded and the distribution of heat throughout the combustion chamber rendered substantially uniform. The dividing of the flow of. the hot fgases and products of combustion over the bridge walls D results in a saving of the bridge walls and adiacent wall androof tubes by submitting the walls and tubes to a lesser amount of-heat than that requiredin the conventional type of tube still operated in a manner to approximate the rate of heat transfer obtained in the present still construction. Obviously the convection system may be divided into two, three or four sections as desired without departing from the spirit or scope of the invention.

Anotherand important advantage obtained in a still constructed as herein described is the reduction in the amount of coking in the tubes which is bound to occur to some degree in pipe stills when employed for treating petroleum products. This decrease in the formation of coke is largely attributable to the increased mass velocity of the fluid as it passes through the tubes in the combustion chamber where the heat to which it is subjected is relatively high.

To group all of the tubes in one section, as has been the practice in the past, might so greatly reduce the heat absorption as to result in the entry of fluid into the radiant tubes at a temperature too low for eflicient operation.

It is thus possible to use the still as a coking still by heating to coking conditions without depositing excess coke in the tubes.

We have thus provided a pipe still having rela-' tively high efliciency in operation through the distribution of the hot gases and the products of combustion whichmaybe expected to provide pro-' longed runs due to reduction in coke deposition combustion chamber, all cooperating to produce a divided flow of the hot gases to attain the objects and advantages and operation herein described. In the event that four such sections are employed, it will be apparent that all of the walls of the combustion chamber. are virtually insulated from outside temperatures upon the outer walls thereof by the presence of the convection' sections; This arrangement, whether the heater be constructed with two or, more such convection sections, greatly aids in maintaining high efficiency in operation by the protection afforded against heat losses in that area of the heater where the temperatures are the highest. In the event that convection sections are'located about all of the sides of the combustion chamber the burners could be inserted in the bridge walls and serviced through a suitable tunnel provided at the base portion of the bridge For some purposes we have found the following routing of" fluid through the several tubes of the sections andthat therefore, three, four or more I convection sections may be providedabout the heater to be particularly advantageous.

routing contemplates the flow of the stock first through the convection sections, next through the roof tubes, thereafter through the wall tubes in the combustion chamber and finally through the bridge wall tubes.

' While we have described our invention by the a combustion cham-' 2. A pipe still comprising a combustion cham-? ber, a pair of convection chambers located one at each of the opposed sides of said combustion chamber thereby to divide the flow of hot gases from the combustion chamber into two streams flowing in opposite directions, radiant tubes in said combustion chamber, and absorption tubes in said convection chambers, the absorption tubes in their respective chambers being connected in multiple and thereafter in series with said radiant tubes, said absorption tubes having an individual flow capacity less than said radiant tubes and a multiple capacity greater than the radiant tubes, the absorption tubes having individually and collectively a greater proportional surface area with respect to cross sectional area than said radiant tubes. v v r 3. A pipe still comprising, a combustion chamber, a plurality of convection sections located about the sides of said chamber and separated therefrom by bridge walls, a series of tubes on the side walls, bridge walls and roof of said combustion chamber, and tubes in said convection sections for heating the stock fed into said series of tubes, said series array of tubes being so connected and arranged as to cause the stock to pass first through the tubes in said convection sections, thereafter through a portion of the roof tubes, thereafter through the side and bridge wall tubes, and finally through the remaining portion of the roof tubes.

4. A pipe still comprising, a combustion cham= her, a plurality of convection sections located about the sides of said chamber and separated therefrom by bridge walls, said bridge walls having a height less than the height of said combustion chamber, whereby hot gases from the combustion chamber may flow upwardly and over the bridge walls and into the convection sections, flue con= nections located at the bottom of each of the convection sections, a series of tubes on the side walls, bridge walls and roof of said combustion chamber, and tubes in said convection sections for heating the stock fed into said series of tubes,

said series array of tubes being so connected and arranged as to, cause the stock to pass first through the tubes in said convection sections,

thereafter in order through certain of the roof tubes, the wall tubes in the combustionchamber and finally through the remainder of the roof tubes.

5. A pipe still comprising a combustion cham= her, a plurality of convection sections located about the sides of said chamber "and separated therefrom by bridge walls, a series of tubes on the side walls, bridge walls and roof of said corn-= bustion chamber, tubes in said convection sections, means for introducing a separate stream of fluid into the tubes in each convection section; means connecting the tubes in each convection section to a portion of the roof tubes to cause the stock to flow through the said portion of the roof. tubes as a combined stream and meansconne'cting the said portion of the roof tubes with said side and bridge wall tubes and the remaining portion of the roof'tubes to cause the stock to, flow there through in the order named.

GEORGE W. wA'rrs.- J WALLACETB. t: 

